The present invention relates to a semiconductor integrated circuit, particularly a semiconductor integrated circuit device for communication comprising an signal amplifying circuit which can select variable gains and a high-gain amplifying circuit for amplifying the reception signal of a wireless communication equipment and also relates to the technique which can effectively be applied to the wireless communication equipment such as a portable telephone comprising the same semiconductor integrated circuit device for communication.
In the wireless communication equipment (mobile communication equipment) such as a mobile telephone and a portable telephone, a low-pass filter and a gain control amplifier are provided for the purpose that a baseband circuit amplifies weak reception signal up to the predetermined level enough for realizing various processes while it is eliminating noise and unwanted frequency signals.
In general, in the portable telephone of the conventional GSM (Global System for Mobile Communication) and DCS (Digital Cellular System), a step amplifier which can change step by step the gain depending on the reception signal level is used as a gain control amplifier. Meanwhile, in the portable telephone of the W-CDMA (Wideband Code Division Multiple Access) system, a linear amplifier which can linearly control the gain is proposed as an amplifier for amplifying the reception signal.